The present invention relates to an apparatus for testing the stiffness of a sheet and more particularly, but not exclusively, to an apparatus for testing the stiffness or crispness of a paper sheet such as currency note.
Prior to the loading of currency notes into currency cassettes for use with automated teller machines (ATMs), it is important to screen the currency notes to detect their condition. In particular, there is a requirement to detect and reject currency notes having holes, or other defects, or having attachments such as tapes or staples. It is also important to detect whether or not a currency note has the necessary degree of stiffness or crispness for satisfactory handling by a cash dispensing mechanism; if it does not, the currency note should be rejected to ensure that it is not loaded into a currency cassette.
An apparatus for determining the condition of currency notes by testing their stiffness is disclosed in European Patent Application No. 0073133. This prior art apparatus determines the condition of a currency note on the basis of the noise made by the currency note as it is bent around a bobbin-shaped drum. This prior art technique has the disadvantage that, as a result of noise interference, incorrect determinations of the stiffness of currency notes may be made.